Prevalence and antibiogram of Extended Spectrum β-Lactamase (ESBL) producing Gram negative bacilli and further molecular characterization of ESBL producing Escherichia coli and Klebsiella spp.

BACKGROUND AND OBJECTIVES: Resistance to a wide variety of common antimicrobials has made the proliferation of Extended spectrum β-lactmase (ESBL) producing strains a serious global health concern that has complicated treatment strategies. The high proportion of ESBL producers among the Enterobacteriaceae and the complex molecular epidemiology with diverse types of ESBL genes are alarming. This study was undertaken to identify ESBL production in various Gram negative bacilli isolated and to further characterize ESBL producers among Escherichia coli and Klebsiella spp by PCR, which were initially screened by phenotypic method. MATERIALS AND METHODS: A total of 722 isolates of Gram negative bacilli were isolated. Presence of ESBL positivity was detected using the double disk synergy test (DDST). Their antibiogram was studied. PCR analysis for β-lactamase (bla) genes of the family TEM, SHV and CTX-M was also carried out using designed primers in 20 ESBL isolates each of Escherichia coli and Klebsiella spp. RESULTS: Among 722 Gram negative bacilli isolated 379 (52.49%) were ESBL producers. The major source of ESBL producers were respiratory tract samples, highest ESBL production was observed in Klebsiella sp. (67.04%). Resistance to multiple classes of antibiotics was observed among ESBL producers. Among ESBL producing genes prevalence of bla-CTX-M (82.5%) was highest, followed by bla-TEM (67.5%) and bla-SHV (57.5%) in the present study. The frequency of ESBL producing strains among clinical isolates has been steadily increasing. Advance drug resistance surveillance and molecular characteristics of ESBL isolates is necessary to guide the appropriate and judicious antibiotic use.